This invention relates generally to sensing, and more particularly relates to optical fiber-based sensing.
Optical fibers can be employed for sensing in a wide range of applications, and are particularly advantageous for remote chemical sensing applications. In a remote chemical sensing arrangement, an optical fiber can be configured to collect an emissive signal at one fiber end and transmit such signal to a detector that is positioned remotely at an opposite fiber end. The emissive signal can in general be, e.g., a luminescent signal, such as a chemiluminescent (CL) signal, and can be transmitted optically by the optical fiber from a sensing location to a remote detection location. This remote optical fiber sensing configuration can be of particular interest for detection of hazardous materials, such as explosives.
Inherent to a remote optical fiber sensing arrangement are several significant limitations. First, the achievable remoteness of the detection function from the sensing location, as well as the detection sensitivity, are restricted by the numerical aperture (NA) of the optical fiber, the optical fiber transmission and bending losses, and the sensitivity of the detector. While the NA can be increased with particular fiber configurations, such as a hollow core photonic bandgap (PBG) fiber configuration, and highly sensitive photodetectors can be implemented, limitations on coupling efficiency and propagation losses present challenges to distributed optical fiber sensing over large areas.